The present invention relates to a group supervisory apparatus for an elevator for selecting and assigning an elevator car (hereinbelow termed "cage" or a plurality of elevator cages) to respond to a hall call.
A plurality of elevators are installed, under group supervisory operation including an assignment system. This system calculates assignment evaluation values for the respective cages immediately after a hall call is registered, selects and assigns the cage with the best evaluation value as the cage to respond to improve operation efficiency and to shorten the hall waiting time. In such a group supervisory elevator assignment system, arrival indicator lamps are generally mounted for the respective cages in the halls of the respective floors to indicate the direction and imminent arrival of the assigned cage for waiting passengers in the hall. Therefore, the waiting passengers can wait in front of the indicated cage entrance without anxiety.
In a congested hall where a number of passengers are waiting, like an entrance floor at the end of the day, i.e., the office-going time, the office-going time is utilized, for example, on the basis of the time and the passenger volume, to assign two or more cages for the entrance floor, or the number of waiting passengers in the hall is detected to assign two or more cages under the condition that the number of waiting passengers exceeds a predetermined value as disclosed in Japanese Patent Laid-open Application No. 58739/1975, thereby eliminating the congestion in the hall.
Heretofore, when two or more cages are assigned for one hall call in this manner, the method of assigning the cages is in the order of the cage with the best assignment evaluation value. In general, when the cage of the best assignment evaluation value is selected for the floor of congestion, such as an entrance floor, there is high possibility that the cage with the shortest time to arrive at the floor of congestion is selected, and the probability that a plurality of cages will arrive at the floor of congestion is increased. Accordingly, at this time, the transportation efficiency is very deteriorated or waiting time is lengthened due to the fact that the cages are sequentially dispatched at a short time interval. In this state, the passengers are boarded into two or more cages and the cages still have sufficient margin of volume, or after the cages depart in a short time interval, a considerable time is taken until the next cage arrives so that the next passengers wait for a long time.
Therefore, there has been proposed a system that, when the congestion of the first floor is, for example, detected, a reference value of the period from when the cage to be serviced previously on the first floor arrives, i.e., reaches an arrival state to when a cage to be similarly serviced later becomes an arrival state (hereinafter referred to as "a reference service interval") is set on response to the traffic volume in the first floor. A reference value of times when a predetermined cage becomes an arrival state and when the other cage becomes an arrival state in on the first floor on the basis of the reference service interval (hereinafter referred to as "a reference time") is set corresponding to the additional number of assigned cages, and the cage having a small deviation between the predicted time and the reference time is selected as the cage of the additional assignment. This cage becomes an arrival state on the first floor to reduce the service of the cages arrived concentratively in the hall of congestion, thereby improving the transportation efficiency.
Further, there have been proposed several assignment methods for the purpose of shortening waiting time by preventing the operation of a plurality of cages in a group simultaneously. For example, there is one system disclosed in Japanese Patent Laid-open Application No. 121186/1987. This system has features for the purpose of eliminating the operation of a plurality of cages concentratively. This system calculates a predetermined evaluation concerning the waiting time of each cage for the hall call generated to select the cage of the optimal evaluation value obtained thereby to respond to the call. When the optimal cage is selected, the generated hall call is temporarily assigned to the respective cages to obtain an index indicating a deviation between the arrival interval at a specific floor at the time of this temporary assignment and an average operation interval for each cage. This index is added to the evaluation value of the corresponding cage as a general evaluation value, and the cage of this general evaluation value exhibiting a preferable value is preferentially assigned to the hall call. At this time, an average arrival interval of the cage from one cycle time in this time zone is obtained, and the assignment control of the cage to the hall call is so carried out as to disperse the predicted arrival time of each cage to the specific floor at the uniform time interval responsive to the average operation interval in the present time zone.
However, since this assigning method uses the average arrival interval obtained from one cycle time but does not use the average arrival interval set in response to the traffic volume of the floor of congestion, it has an effect of dispersing the cages to be able to respond to the hall calls of all the floors in a short time, but it is scarcely said to have an effect of improving the transporting efficiency of the floor of congestion compound to a system for servicing the hall calls of the floors of congestion by assigning a plurality of cages to the hall calls as described above.
Further, in the above-described assignment control, the reference time for arrival of the cages at the floor of congestion or the specific floor is set by using the average arrival interval obtained from the reference service interval set in response to the traffic volume of the floor of congestion or one cycle time. The cage having a small deviation between the arrival predicted time and the reference time is merely selected, but no procedure is determined for the operation of the assigned cage after the assignment. Thus, the assigned cages might not arrive at the floor of congestion or a specific floor within the reference time, and there arises a drawback that the improvement in the transporting efficiency of the floor of congestion and the reduction of the waiting time due to the prevention of the operation of a plurality of cages concentratively cannot be always performed.